After working with SourceSafe for a few years, working with SourceGear's Vault for a couple, and TFS briefly, VisualSVN was recommended to me.

This engine was extremely easy to set up,  and even easier to update for patches. This was the main contention I had with Vault. The visual studio plugin is $49, but "It Just Works", and in my opinion is worth the expense. This is especially true considering the server itself is free.